G. Christopher prefers The Better Man has an earlier placement but also notes it was intended as 2 years after TMP. The year is not stated in the book so I left it where the Pocket Timeline placed it which is around 2 years after TMP.

Actually the year is established pretty unambiguously in TBM. The story explicitly states that McCoy was on Empyrea in 2254, and he's suspected of being the father of a young woman who's just turned 18. Those dates are mentioned specifically and repeatedly in the text. Allowing for 9 extra months, that pretty much pegs the book as falling in 2273. (There are some references to the visit being 20 years earlier, but those are alongside numerous references to it being 18 years, so I assume there's some rounding going on.)

And the bit about coming 2 years after TMP is really only mentioned in the historian's note; it has no relevance to the text proper. The author's intent is that the book takes place between 18 and 20 years after 2254, i.e. roughly 2273.

Actually, it seems like the author had two intents which are now contradictory, based on what's being described. (I have to go by this, since I haven't read The Better Man.)

On the one hand, the novel is supposed to be two years after TMP. On the other, it's supposed to be 18 years after 2255...which (at the time that book came out) would've been the same thing, based on official sources. The date for TMP has moved forward since then, but I would personally go with Jsplinis's instinct to maintain the novel's placement relative to TMP.

It's not as if many of those other novels don't also have calendar dates (stated or implied) that are now problematic, and I imagine that if TMP had already been thought of as taking place in 2273 at the time, McCoy's visit could've/would've been described as occurring two years later.